Method and equipment for motorway control

ABSTRACT

The method and the means concern a system for control of motorway traffic, with focus on access control. The network characteristics of the traffic, according to the invention, is treated by traffic control functions based on the traffic as well as the access itself, as at the closest section upstream the access, and at connected parts of the road network. The invention goal is safer traffic and an effective utilization of the motorway. The system is creating possibilities for a dynamic traffic management with control of traffic flows. A smoother and better controlled weaving process is effected by preparatory actions and the functions create more margins, as well in space as in time, for the performance of the usually complicated and dangerous driving procedures on the motorway. Modern information technology is used as a means for carrying out the invented solutions.

BACKGROUND OF THE INVENTION

Short Information about the Invention as System Controlled Access (SCA)

The system controlled access is designed by several coordinated steps.Actions are taken at the road net on different distances from the givenaccess point. Far upstream, traffic control actions are introduced, thate g might limit average flows in to SCA, i e for an average time period,some minutes or less, a controlled amount of cars will arrive. Duringthe travel towards the motorway access, those cars however might packtogether to various dense “car-packets”, which implies that during shorttime periods of less than a minute, large differences from the averageflow might arise. Those differences have to be considered at e g closerpositioned accesses, not allowing many cars at the access at the sametime as there are a package of dense traffic on the motorway. Otherwiseall the cars haven't space enough for weaving, and the traffic collapsesresulting in queue build up and high risk for accidents.

By regulating the access traffic in relation to the motorway traffic,the traffic density is smoothed for the downstream motorway link.However there are many factors working in the opposite direction, whytraffic successively will distribute according to statisticaldistributions. Thus one might measure a certain traffic distribution atone spot on the motorway, which is different from the trafficdistribution some kms further downstream. Differences in detailedtraffic distribution arise also if there are no access or exits inbetween. That means that one often has to consider newly and closelyarisen variations, when striving for an effective traffic control.

So there is also a need for a final control at the waving area toachieve a safe and efficient traffic access. An important part of theinvention considers that last phase of the access control.

The invention can be regarded as a system of actions on four differentlevels. The first level is “Access control along a motorway” and isbased on traffic management of a road-network, considering variousaccess roads, as other motorways, connections to city street-networketc.

The second level is “preparatory weaving”, which is performed on themotorway upstream exits and access-roads.

The third level is “preparatory actions”, which are performed justbefore the “ramp”.

The fourth level is the “local level” at the position of the ramp.

The four levels can work together and combine to an efficient and safeaccess traffic. But compared to to-day situation, every level by itselfcan be implemented resulting in improved access control. The inventionconcerns a system-based improvement of access traffic control, where thedifferent levels can be implemented one by itself, or in combinations tovarious extent, or successively at different occasions, possibly assteps in a planned expansion, or within a given short time period toobtain a more direct cooperation of the applied levels.

TRADITIONAL ACCESS CONTROLS

The most used on-flow “control” is free weaving of traffic from theaccess road into the motorway, but with certain rules giving themotorway traffic priority, i e the cars from the access-road shouldadapt and weave into the gaps between the cars of the motorway. When thetraffic flow on the motorway is close to its maximum, there aren'tenough safety margins to put cars into the small existing gaps. If a caranyhow turns into such a gap, the driver wants to start braking toincrease the distance to the car in front of him.

The car behind, then has to brake even harder, partly because his gapshouldn't decrease and partly because the distance gap was too smallalready from start. Simply said, the braking need has doubled. Then ifmore cars are weaving into gaps between the following cars alreadybraking to keep their safety distances, then the result soon turns intoa traffic collapse with queue build up and large risk for accidents.Similar collapses occur also when the motorway traffic is less dense,but the access traffic flow is higher, giving the total flow above theaccess weaving capacity.

TRADITIONAL “RAMP-METERING”

The concept of ramp-metering is often described as a way to limit theaccess flow to the ramp, not allowing more vehicles to enter than whatgap space there are on the motorway. When there are periods with lowertraffic flow on the motorway, more cars can be allowed to access, and ifit is very dense traffic on the motorway, no cars are allowed and so on.The access is regulated by traffic signals. If there are too many carsin a row on the access road, they will be lined up in queue, and one cara time is allowed, when the traffic light signal turns green for somesecond.

The problem with ramp-metering is that it is not operating that welladapted to the traffic. Certainly the motorway is equipped with sensors,positioned just upstream the ramp (e g a couple of hundred meters) andthus measure the traffic at that position. But there are two problems,when one wants to utilize those measurement values for controlling theaccess traffic. One problem is usually too long measurement periods e ga minute. That implies that before the measurement period has ended, thefirst cars have had time to run for almost a minute, meaning that theyhave passed a distance of 1800 m (L=v*t) at a speed of 110 km/h. Most ofthe cars thus have already passed the weaving area before even themeasurement period has ended. That measurement intended for givingknowledge about how many cars, that are on their way to the weavingarea, for the intended succeeding control of the ramp-meter according tojust that traffic. The other problem is that the light signal has to bepositioned far upstream on the access road, giving the stopped cars along enough distance of acceleration to reach the speed (110 km/h) ofthe motorway traffic. They should have the same speed as the motorwaycars to be able to weave into the motorway traffic in a smooth safe way.It means that controlling the ramp-meter according to the measuredvalues, it will take further some 20 to 30 seconds (t=v/a), before theaccess road cars have reached the weaving zone, i e the traffic, thatnow is on the motorway, is quite another traffic than has been measured,and the measured traffic has already passed.

Thus the measurement should be carried out at least the distanceL=v*t=v*v/a==v²/a upstream of the weaving area.

It seems that those traffic engineers that use ramp-meters, haven'tunderstood the problem. Accordingly there are some secret magic aboutthose algorithms and methods used on the measured values to optimize inwhat time period the cars should be allowed to pass the metering signal.Generally the methods also use more than one measurement period value,to reach their results, which means that they are trying even harder toadapt the access traffic to that traffic on the motorway that havepassed since still longer time ago.

OTHER KNOWN TECHNIQUE

In the Swedish patents 9203474-3 and 9501919-6 methods are described forpredicting traffic and detecting incidents and traffic collapses. Thosemethods are generally applicable for traffic management on the wholeroad network, and are also useful at access control. Those methods arepostulated known, and when prediction and queue-detection etc arementioned in connection with the present invention, those methods aregood examples of how to perform such matters.

Access control by ramp-metering has been used for a long time period,not least in U.S. The methods have their deficiencies and is generallynot really operating in that way as it is described. That was describedin the section Traditional “ramp-metering”. Here we shall discuss somechosen known examples on methods, which have been suggested for use inconnection with access roads and lane changes.

There are ideas on building “car-trains” or platoons of cars onmotorways for increasing the capacity very much. The cars are going tobe automatically controlled, driven very close to each other (e g ameter), and be using an advanced mutual communication of data. Thevehicles will be electronically connected to a train, which is supposedto travel very fast and safety. Also the processes of leaving andjoining a train will be complicated, as well as changing lanes amongautomatic trains or platoons. This is supposed to be handledautomatically by interactive communication between neighbouring cars,that negotiate for allowance and support from others for performing thedesired actions. Standardized communication protocols are suggested forthe automatic process.

At the access to an “automatic motorway” the cars are sendinginformation about their destinations and are receiving detailed journeyplans from the “road-based system”. Those plans are then automaticallyfollowed by all the cars all the way to their respective off-roads fromthe motorway.

The present invention has another function and is primarily created fordriver-controlled cars. So the inherent functions are open fordifferencies in driver behaviours, and takes into account the naturalstatistical variations in traffic. The basic parts of the invention canbe applied with to-day cars, and is not requiring the advanced vehiclesystems and methods, which are needed for the ideas of “car-trains”.

In the patent DE1943596 A1 a method is described informing car driverson recommended positions along the lanes. A light-line is presented infront of and behind the car. In the position the car should be, a gap isgiven, i e the light-line is off in this interval. The off-light gap ismoving forward with that velocity the control system is determining. Thepresented design with the light-line position in the middle of the lane,makes an impression of being expensive, brittle, expensive to maintainand giving failure mode problems, as non-desirable gaps are given,wherever any part is broken.

The described access control is treating situations, when the flow ofthe motorway and the access road together is low enough giving a totalflow below the capacity of the motorway. Then that invention mightsomewhat correct the relative positions of the cars in such a way, thatcars are not reaching the weaving point at the same time, but withacceptable gaps in between. To-day that process is performed by using aramp, where the cars on the access and the motorway are travellingseveral hundred meters in parallal, and the drivers are watching eachother optically and controlling their speeds to adapt to the gapsbetween the cars before weaving.

The real traffic problem arises, when there are too many carssimultaneously on the motorway and the access road. The problem mightarise already for very short term flow peaks (one or a few tens ofseconds). This is usually happening at rush hours at large cities. ThatDE-patent is not solving this or other problems. However the traditionalramp-metering is a trial to treat that problem, and the presentinvention gives solutions on that and related problems.

In a patent DE4238850A1 a method is described for informing drivers ontwo lanes how to weave, when the two lanes turn into one lane. It isproposed to be done with a sign, showing a surveillance model image ofseveral car positions in respective lane during the weaving phase. Theimage is illustrating the weaving for a time sequence of several frames(7). It is an obvious problem for the driver to understand which car ishis, and then to understand what to do accordingly. This is a generalproblem, when one wants to present selective information to individualdrivers. How to tell one individual that it is just for him the messageon the sign is directed.

In the present invention methods are given where this problem is solved.

THE BASIS FOR THE PRESENT INVENTION

To achieve a good solution for access control to motorways, a wholisticprocess, a system solution, is needed. In its first place, it is notevident that one always should allow as much traffic as is possible froman access road to a motorway. It might imply that the motorway is almostfilled up by traffic at the next downstream access, why one at thislater access, cannot allow that amount of traffic one wants and that isneeded to avoid long queues and large traffic problems at theneighbouring road network.

During morning rush hours the traffic grows dense on the access roadscloser the town city. It means that the risks for traffic collapse andqueue build up is larger closer to the city. To-day it is regularly longqueues on the entrance routes of the large cities of the world. Usuallythe queues are causing larger problems the closer the city they are. Thereason is that the road network is more dense there with more roads andwith larger flows of traffic connected to each other. A queue that buildup on one road, is easily growing backwards to connected roads, and isthere blocking or reducing the passability also on those roads, which inits turn causes even faster queue build up on those roads and fastspread of queues further across the road network and so on. It is notunusual with large network areas of reduced traffic capacity, caused bytraffic flows unnecessarily blocking each other by queues.

From traffic management point of view, it might be much more beneficialto distribute the traffic, in such a way, that queue build up to alarger extent is occurring at the more peripheric areas, where the addedblocking effect is less. By that the total queue time can be reduced,and in several cases the traffic situation should be remarkably better,and the queue build up almost disappear. A tool for achieving suchpositive effects is obtained by the “System controlled access, SCA”,which takes care of the large scale functions described above and alsothe detailed access control including the design of ramps and equipmentsfor more efficient and safer motorway access processes.

An example on increased safety is obtained, offering the drivers helpfrom the system, defining and appointing certain driver roles in thetraffic interaction processes. To-day it is required that the driversmutually agree on the way to interact e g agree on who to drive first,or who to let a car in, that wants to change lanes. Often the drivershave only a very short time for reactions, combined with poorpossibilities for communications, why misunderstanding is easily turningup, causing dangerous situations. Traffic rules are helping of course,but they are difficult to evaluate in short time in complicated criticalsituations and borderline cases. Therefore the present invention alsoincludes system functions and equipments for role identification andappointment.

FIGURE DESCRIBTIONS

The invention is shortly described with reference to FIGS. 1 and 2.

FIG. 1: A traffic management system is fed with traffic information fromsensors, S, at various positions along the motorway, on accesses, P1-P3,and possibly at the connected road network N1. The management systemmight be more or less advanced. It might have functions for continuouslycalculating and predicting of traffic on the given road network. Itmight have analysis functions for comparison of traffic streams withtravellers need for road capacity etc. During rush hours the capacity ismany times inadequateat at several links and nodes at the road network,and traffic can be distributed in a way utilizing the road networkbetter and reducing the traffic problems. Values on goals for trafficflows can be determined on motorways and access roads. Goals can bedetermined adapted to various traffic conditions and be given certainvalues over the day. Those are values, that reduce traffic problems, ifthey are under control.

Access roads can be given flow rations, which prevent overloading alongthe motorway. The goal values might be regarded as average guide-lines.In reality the traffic is fluctuating and short term variations of themotorway flow might be measured at the nearest upstream S and/or at theexit in A1, and be used by the local access control at P3, for dynamiccorrection of the onflow in relation to the ration. The correction isdetermined in C1, P3 or A1 and should be based on a prediction of theflow at the access, knowing the upstream measured result.

The distance L1 from upstream S to the access, must be long, as theonflow control requires time for actions. That means that there will bea need fo correction of traffic density, gap distances, of the motorwaytraffic travelling to the weaving zone. Information considering gapdistances is given by the information means I1.

Finally the system can be expanded by adding weaving information by I2,which informs individual cars about their respective roles in theweaving process. That will reduce insecurities and risks in the weavingprocess.

FIG. 2 is a diagram of the exit control, with the introduction of a“Middle lane”, Me. To the left, upstream in the figure, there are threecars illustrating the intention of changing lanes. The car in the leftlane indicates that it will turn to the exit. The first car in the rightlane also wants to turn. The other car wants to change to the left lane.The small circles at the front and back of the cars illustrate activatedblinkers.

Arrows in the lane show how the cars change lanes and how the cars inthe right lane alternatively turn to the exit or continue along themotorway, where Me and the right lane join to continue as the rightlane.

The exit equipment A1 has sensors, S, which detect turning informationof the cars, and information means I, which inform the cars about theirroles including assigning of lanes. A1 delivers information about themotorway flow, based on how many cars, that turn, and that informationis utilized for correcting the goal flow, the ration, at downstreamaccess control.

DESCRIPTION OF THE INVENTION

From traffic management point of view, we want a controlled distributionof the access traffic along a motorway. Assume that we have got asituation with increasing traffic towards the city, and that we have gotan access road (P3), where traffic regularly is collapsing at themorning rush hour with long queues as the result. A traffic managementsystem analyses the traffic situation on the road network, and producesa desired distribution of the access flows of the different accesses.The requirement is also to avoid queues on the motorway, i eextraordinary large traffic flow peaks should primary be taken care ofat the access roads. The given access (On0)is in this example the narrowsection, the bottleneck that traffic has to pass before spreading outthrough the consecutive exits.

Consequently there is an updated access control setting, as a basis forevery access, and that control is giving the desired trafficdistribution and is preliminary bringing the bottleneck at (P3) beingpassable by the motorway traffic without collapsing into a queue.

The SCA operates from an upstream access (e g the third, (P1), countedfrom (P3) in the following way.

A traffic signal at the access road is given a first setting, thatlimits the access flow to the given predetermined value. Measurementsand controls are performed based on a relatively short measurement timeperiod (t1), less than a minute. If the access demand is lower than thepredetermined value during the time period, the extra flow is given asan additional flow portion to the closest downstream access or theaccess that needs it more. If the motorway flow instead was larger thanthe predetermined value, the result might be larger total traffic volumeafter the access, and the succeeding access and/or accesses furtherdown, are then assigned corresponding decreases of their allowed accessflows. In this way the deviations from the goal value are correctedsuccessively along the motorway, and downstream accesses (p2 to P3) aresuccessively given information about what traffic flows can be expectedand what corrections to be done from their assigned access flow ratios.

There are generally two reasons for arisen deviations along themotorway. One reason is the deviations in exit traffic between twoaccess road. The other reason is deviations because traffic is bunchedtogether in various ways, especially pronounced for long distancesbetween accesses.

At upstream accesses the total traffic inwards city is generallyremarkably lower than the capacity, also when there is some extratraffic. So we study (P3) more carefully, as this is the narrow seciton,where it is desired to pass the maximum flow, i e utilizing the maximumcapacity.

Now there is a traffic management system, which controls that trafficgoing in to (p3) in average is at the right level, both on the motorwayand the access. Let us also assume that there is a queue on the accessroad, why there is a need for utilizing the max capacity during the“study period”. The first problem now is that the motorway traffic isn'tabsolutely known in detail, when allowing the cars at the traffic signalat the access road. There are packets with a bit more dense traffic andthere are packets with less dense traffic. If now cars are allowed fromthe access road according to the average distribution, there is a riskfor traffic collapse, when there are dense packets on the motorway, andnot completely utilizing the full capacity, when there are less densepackets. The more knowledge about the traffic long enough in advance,the closer the traffic flow can be matched by the traffic signalcontrol.

PREPARATORY ACCESS CONTROL

If the closest upstream exit is positioned that far upstream, that ameasurement on the traffic can be obtained in time, before the relatedaccess traffic has to be allowed by the traffic sign, then very muchwould have been achieved. A design of the road network structureconsidering this matter, would be helpful, where it can be implemented.The present exits and accesses are not always fulfilling thatrequirement.

A measurement of traffic using short measurement periods at exits isanyhow giving opportunities, in second hand decreasing the access flow,not to make packed traffic ahead worse, by further adding of accesscars.

A measurement of traffic just before the access connection (some hundredmeters) might be valuable for controlling the the final part, the actualweaving process.

There is a possibility to design the ramp, giving the car on the rampinformation, before weaving, about not continuing for the weaving, butcontinuing along the ramp, turning off into an exit road going back fora new trial.

It is remarkable that dense traffic motorway ramps haven't thatopportunity already to-day. There are arisen dangerous situationsalready, when cars on the ramp don't find any suitable gap, and arebreaking to find a late gap, which might not arrive. When the end of theramp is close, the driver is caught in a dangerous situation, where heis throwing his car into the motorway, - often into a too small gap andwith a different velocity, or he might continue on the road shoulder. Itmight work out for this driver. But there is no guarantee, that it willwork out for the followers. The result is often sudden brakings on themotorway, which in turn might cause accidents. Implementing a returnroad from the ramp, thus would be another action offering help in thetraffic management work.

The weaving process is in itself a risky process, especially when onewants to utilize the capacity at maximum. The margins then willaxiomaticly be correspondingly small. Tools facilitating that processimply more safe and more efficient weaving. The following theoreticalreasoning is a pedagogic example. Imagine the motorway and the accessconsisting of small platforms carrying respective car, and a mechanicalsystem managing the movement of each platform. Then it would be a simplecontrollable task for a system to successively adapt velocities and gapsof the platforms in such a way, that weaving the platforms from themotorway and the access, would be carried out in a very safe andefficient way.

In the following we shall describe methods, which are of help to createa process that is reaching further towards the described theoreticalexample than what the established access processes of to-day are doing.Instead of mechanical movement systems we will use informationtechnology as tools.

For synchronizing the motorway traffic and access traffic, one way is toidentify, for each access car, that motorway car (B), which is to let inthe access car (A). Also there are installed signal means at suitableintervals along the motorway and possibly the access. Those means can bedesigned in various ways and be positioned in various ways e g hangingabove the road, attached to poles at the roadside etc. Here a design isdescribed in more detail as an example.

On poles, similar to road signs, information signs are put along themotorway. They can be turned on and off and possibly change information.They are screened and directed backwards to the traffic flow. They shallbe able to switch on, when the car ahead of (B) is no longer seeing theinformation, and be on as long as (B) sees it. Successively the nextsign is switched on and so on. The signs can be positioned more or lessdense on such a distance, that principally one sign is always on and canbe read by (B). The car (C), which is following (B), experiences thatthe signal is not meant for (C), as the sign is turned off when (B)cannot see it any longer, which is at latest when (B) is passing thesign.

Information in a simple design, can be a lamp, which is on for (B), when(B) should decrease his velocity, either for increasing the distance tothe car ahead or for adapting the arrival time to (A)'s arrival time tothe weaving zone. Car (A) also might get corresponding information,meaning reducing his velocity for avoiding running away from his “gap”.It is not always easy for (A) to do a final correction, while driving inparallall with the motorway, and perhaps not even seeing if he might betoo far ahead or back.

There are respective measuring means on the motorway and the accessroad. By help from those the (B) -car is selected due to the predictedarrival times of the cars. This process performs close to what ourtheoretical mechanical model was doing. There are however variouspossibilities to improve the function.

Instead of just switch on and off a lamp, information can be made moreclear. It can be symbols, describing how much the gap has to beincreased to the car ahead, possibly related to the desired and presentsize, e g by a line-symbol of the desired gap, wherein the position ofcar (B) is included with a symbol, possibly with “alarm information”(blink, colour, arrow, lined area etc.), amplifying the need for action.One can show that a car will weave in front of (B) in different ways e gwith a symbol arrow into the gap between (B) and the car ahead, possiblycan a model of the access ahead be shown, including coloured arrowsshowing (B) and (A) travelling towards the weaving zone, and (A) turninginto the gap in front of (B).

One can give dynamic velocity information possibly also to (A), managingthe cars to a synchronous weaving. One can add text. It is importantthat information is easy to apprehend quickly and withoutmisunderstanding. At dense traffic the time gaps between cars are small,about 2 seconds, which isn't much time to grasp the information. Whenthe gap is increased to 3-4 seconds to let a car in, the distance willbe about 100 m (at 110 km/h), which on the other hand is a long distancefor seeing detailed information. Therefore it is better there aresuccessive information means ahead, that are successively turned on andcreate a kind of repeated information to (B). One can utilize the roadsurface upstream the access point to mark the recommended gap betweenthe cars e g by arrows, lines etc. They can be painted on the roadsurface. Usually one should be able to see two marks, while a car in(B)-position should be able to see three marks, possibly the designincludes interchanging each other mark to look alike. Then (B) wouldfind his gap more automatic without the need for “counting” marks.

Instead of the roadsign type of information, one can design theinformation presentation using searchlight, lightening the road sectionin front of the given car. The way of lightening the roadsurface,possibly with sweeping light, and possibly with light reflecting markson the roadsurface, offers possibility for the driver to obtaininformation straight ahead from that area which he anyhow has got in hisnatural view.

Cars equipped with ICC, Intelligent Cruise Control, or distance keeperto the car ahead, can obtain information directly to the car equipment,that they are e g (B)-car and what distance to select and also thevelocity. That equipment can present and/or automatically bring out therequired gap ahead of the car.

A safety increasing effect is also obtained by lowering the speed. Abovewe saw the problem of short time for performing control, as results ofmeasurements. The cars had time to run far with 110 km/h. Lowering thespeed is suitably performed dynamically, when traffic on the motorway isgetting dense. Lowering levels down to 70 or 50 km/h, is performed inthe usual way in steps. The position of the access control signal canthen be chosen remarkably closer the wearing zone, and the measurementon the motorway and the sign means can also be placed correspondinglycloser to the access point. The adaption of gaps, which now can beshorter, and the weaving process can be performed at a more calm speed.The following is suggested for using dynamic velocity adaption. Thespeed on the motorway is high at free flow and less dense traffic e gduring most of the day hours. The suggested tools are used whensuitable. At more dense traffic the velocity is decreased and the giventools being adapted to this situation are used more fully.

Detecting the car positions can be done from the roadside, possiblycombined with the signal means. It can be performed by known types ofsensors. One can also use simple sensors, which only detect cars passingand thus trigger the signal means “on and off”. They can also simplymeasure time gaps between cars and by that survey the adaption of thegap. When car (B) is defined, there are simple methods to survey theprocess down to the access point. A method is based on prediction whencar (B) will reach a certain position. Corrections of predictions can bedone successively, dependent on measured deviations from the predictedvalues. Applying said methods, one can make preparations in time beforearriving to the ramp, for allowing an access car (A) to weave in aheadof a motorway car (B). If starting at about 660 m upstream, the (B)-carhas got 20 s, and then the (A)-car also has got that time for his lastpart of transportation to the weaving zone. Lowering the speed, the carswould have more time to use, and then their respective distances can bedecreased. One way doing the final choice of (B), would be firstallowing (A) to pass for the access, and then measuring the status of(A) at an intermediate station and from that predict the arrival time tothe weaving zone, and thereby also select the suitable (B)-car. Theallowance of the (A) car to pass, is determined from still furtherupstream measurements, offering a predicted average density for a shorttime period. Within such a defined short time period car packet, thereis space for an (A)-car, seen over the whole packet. The methods above,are aiming at distributing the gaps between the cars in a bit differentway, giving a real space for (A), when (A) and (B) are arriving to theirweaving zone.

That should also be performed in a smooth way, not risking that thefollower car (C), is running into (B). Simplifying for (C) and alsoother following cars, those cars can also be given information about e gbraking to keep a safe gap the car ahead. An alarm signal, informingabout the activity of the car ahead in the preweaving process, cancontribute to an increased safety.

Car (A)-control

Car (A) can also be given a more accurately controlled transport byobtaining a successively updated information about desirable changes tosynchronize to the weaving gap. In present systems cars (A) haverelatively large individual differencies in travel times form theramp-meter signal to the weaving zone. It is because the acceleration iscarried out by large individual differencies. Also the performance ofvarious vehicles e g heavy trucks, play a role. It implies that alsowhen the (B)-car is accurately controlled, regarding its adaption of thegap distance, the (A)-car might arrive far ahead or behind the createdgap.

In one embodiment of the system, the (A)-car is given successiveinformation about its relative position related to the expected gap. Onemight e g show two parallall lanes, where the expected gap is markedstatic on the left lane, and the predicted final position, based onactual velocity status, on the right lane. A line from the middle of thegap, across the right lane is marking the target line. The symbol of thecar (A) might e g shine blue with an arrow up towards the gap line, whenthe relative position of (A) is predicted to be behind the gap. While if(A) is presented ahead of the gap, the symbol is shinig yellow and thearrow is pointing downwards. When the (A) is indicated just across thegap, the symbol is shining green. An arrow also on the green symbolindicates that (A) should change his velocity accordingly, for keepingthe position.

Principally the tasks can be divided, giving (B) the main task creatingthe gap, and (A) the task adapting his arrival time to be in synchronismof the gap.

Standardizing the velocity process for the access cars, there would begain, as the drivers successively are learning to follow the givenrythm.

Another way to see the need for control of (A), is by watching the flowof (A)-cars. At dense motorway traffic, one perhaps let through 600cars/h, i e one car each 6 seconds. Then it is 12 seconds between afirst and the third car. That time difference might easily be absorbedby differences in acceleration, why the three cars might reach theweaving zone tightly together. Then there will be no space for all ofthem weaving smoothly. If the allowance of (A)-cars is even denser, yetlonger platoons of (A)-cars might reach the weaving zone tight together.Thus it is not sufficient with the present ramp-meter system functions,for reaching a steady predetermined access flow to the motorway. Thereis a need for a complementary system. On the other hand, a dynamicmanagement system for (A)-cars would replace the present stereotyperamp-meter system. Often the access cars would be managed up to themotorway individually matched, without any need for stopping at any redsignal. A stop might be regarded as one of several steps of differentvelocities, included in the dynamic speed adaption.

Preparatory Weaving

Another type of preparation for downstream accesses and exits, includesthe lane changes between the left and the right lanes of the motorway.The drivers regularly want to carry out those changes early in time.Weavings between lanes cause an increased accident risk and cause adecreased capacity for the road segment. Simply expressed, the carchanging lanes needs reasonable space simultaneously in both lanes justwhile changing. There is a natural need for cars in the left lane tochange for the right lane upstream the exit ramp, when they are going toleave the motorway. After an access there also is a need for cars goingfor a longer distance, to change from the right to the left lane. Thenthey avoid being involved in the near access processes. Also aneffective dense traffic in the left lane is necessary, for allowing amaximum number of cars from the following access road, and offering thecars space enough for weaving into the motorway.

Special weaving zones might be designed at the mentioned road segments.There is one segment in the position between an exit and the followingaccess, where it is advantageous to weave from the right to the left.There the exit has caused gaps, related to the cars that turned off.Then there are gaps in the left lane open for weavings from the right,while the right lane isn't completely filled up.

The extra capacity can be used for weaving to the left, increasing thepossibility for added flow from the following access.

After an access and before an exit there are needs for weaving in bothdirections. Those who will turn off at the nearest exit and are drivingin the left lane want to change to the right lane. Several of the newlyaccessed cars want to change to the left lane. If both lanes areutilized at a maximum, there are no space for weaving. However thosecars going to leave are anxious to change, and then the risk growslarge, when they force themself into too small gaps in the right lane.The process can be made safer by adding a special lane, an extra lanewith related traffic rules. The extra lane is positioned between theleft and the right lanes, by (easiest) the right lane bending out givingplace for the intermediate lane (int). Continuous marked lines force thecars to stay in their respective lane as a start. Then leaving cars,(A)-cars, are allowed to change from left to int. lane. Before the shiftsuch a car should indicate the shift by the right blinker. The carbehind in the right lane, (B)-car, might indicate a shift to int. lanewith his blinker and weave into int. lane after (A). Also the car after(B) can be given possibility to select int. lane, if he e g wants toweave further on to the left lane. The closest car, staying in the rightlane, (C), has to watch for and keep the safe distance to his relatedcar ahead, which now is in the int. lane. The car called (B), thefollower, if aiming for the left lane now weaves into the gap; that hasbeen obtained in the left lane by (A) leaving. The car that was behind(A) in the left lane, is keeping the gap to let in (B), or a followerfrom the int. lane (or possibly later on a car from the right lane). The(C)-car watches the safety distance to the car ahead in the int. lane.In the next phase, 2, (A) and possibly another car in int. lane weaveinto the right lane in the gap ahead of (C).

The rule utilized both here at an exit and at an access, is that thefirst weaving car (A), is supplying a signal (blinker). The car behindin the neighbouring lane, car (B), is responding with a signal and isturning after (A). The other cars keep their original safe distances,also if the car ahead now is in another lane, until the weaving processis ready.

Local Access Control

In the area, where the access road is connecting the motorway and (A)and (B) can see each other, there is a final correction of speed anddistance gap to achieve a safe and effective weaving process. If thepreparatory process has worked out well, there is not very much left todo. One might however consider further tools to make also this processeasier, especially if the first step didn't work out quite good.

Below there are presented a number of methods and tools. Most of thosecan be of help, also if the previous methods haven't been used.

Signals for indications of the roles (A) and (B).

When (A) and (B) are seeing each other on the ramp, the access controlsystem can help defining (A) and (B). Upstream the weaving zone, at the“isolated” part between the ramp and the motorway lane, where it is aline separation, it is shown for (A) and (B), possibly with a commonsign, the own position related to the other's. (A) might be presented anarrow symbol, indicating where the gap and the (B)-car is positionedrelative the own position, and by that identifying the actual gap and(B)-car.

Connected to the above method or as an alternative, (A) might takeaction to get the position (on the ramp) definitely ahead of that car,being a (B)-car, and after that giving signal with blinker, showing thedesire to weave into that gap. The car behind replies with his oppositeblinder (the right one at right driving), accepting the role as (B)-car.

As a continuation of any of the above methods, or as an alternative, onecan regulate that (B), as soon as possible adapts to (A), and make theroles evident by the right signal, fulfilling the shift of lanes to theramp. By that it is achieved, that first the weaving is performed to theramp, where the traffic is not that dense, and that the (A)-car and the(C)-car easily understand, who is the (B)-car. Then (C) has got furthertime for expanding the gap to (B), without an immediate risk runninginto (B). Not until the end of the ramp, the “couple ” (A) plus (B) istogether weaving into the expanded gap on the motorway. (A) then has gottime to get the right position for the gap, (B) to expand the distanceto (A), and (C) as said, expanding the distance to (B). So at weavinginto the otherwise dense traffic on the motorway, in this way asufficient large gap has been created.

The ramp should with this method implemented, possibly be adapted by adesign of two weaving zones. First an early one on the ramp, where (B)is weaving, then one more at the end of the ramp, where (A) and (B) areweaving. Further more weaving from the inner motorway lane to the outerlane (right) should be forbidden during the local and possibly thepreparatory access control process. As a further safety action, the rampmight be designed with a returning road lane for those drivers on theramp, which anyhow couldn't find their safe gap for weaving. Without theabove presented methods and tools, i e as it is to-day, the returningroad should be of still more help.

One more safety action is the introduction of dynamic speed controlbefore the access. Finding that in spite of all actions, there will beproblems, one can reduce the speed remarkably, and thereby decrease therisk for more serious consequences.

Examples on Related Exit and Access Control

Often the exit and access of a motorway are connected as a couple toother traffic links, with the exit generally upstream. The distancebetween the exit and the access might be relatively short, and there areadvantages in utilizing the exit control also as as a preparatory accesscontrol. The following example is illustrating how that can beperformed.

This example is similar to that described in “Preparatory weavingcontrol” above.

As a start the exit is modified, utilizing the beginning of what laterbecomes the exist, as a third lane. The cars in the right lane willexperience a lane division, where the system can distribute cars betweenthe lanes. Cars in the left lane at this exit waiting to leave at theexit, signal as an (A)-car and shift to the int. lane, when (B)-cars orthe system has prepared space in the int. lane. Cars in the int. lane,arriving from the right lane, are now given prepared space in the leftlane. This is done by identifying certain cars as (B)-cars, i e suchcars that should let in cars ahead.

At the end the right lane is divided into one link that continue as theordinary exit, and another link that is combined with the int. lane, asa continuation of the ordinary right lane.

At the system estimation of the car density in the right lane, thosegaps are included, that will arise after the weaving of cars to the leftlane before the related access. Then for this access, the informationthat was obtained already at the exit, can be used for control of theaccess.

In this example, those cars are prioritized, that originally are in theleft lane and are going to leave at the exit. For support in the weavingprocess, they ought to give signal early in time. The system can detectthe signal and give support by managing the choice of the right lanecars for the int. or the right lane. Added to that there is the need forutilizing the left lane, to be able to achieve a maximum of space in theright lane, for the cars arriving at the next access.

Controls and Surveillance

When parts of or the whole system is implemented, there should beincluded an internal surveillance control function. Its task isregistering from measurements the real result of the actions, for asuccessive updating of functions and algorithms, by which the system isadapting and improving. That can partly be done automatically built inthe control process, and partly by the means of failure reports, alarms,statistical result reports etc.

The measuring stations, that are directly motivated by the purpose ofcontrol should be useful also for the surveillance function. Howeverthere might be a need for complementary measuring stations, e g afterthe ramp, which are delivering traffic status, showing the result of theaccess control, i e the effectivity and safety of the traffic out fromthe access process, and the traffic meeting the downstream strains.

There is also a need for using the consecutive measurements to detect,if and when the control functions after all, are not giving the requiredresult. E g when the system from measurements is predicting (ordetecting), that a (B)-car is breaking rules, not giving the requiredgap, or the (A)-car on the ramp having engine failure or is missing thearrival time, then a dynamic velocity sign decreasing the velocitybefore the weaving zone can be a measure to decrease the accident risk.Another measure can be interrupting the (A)-car's process and managing(A) back on the return road.

Examples on Embodiments

The system can be looked upon including four levels of actions asdescribed on the first page, and one interesting example is thefollowing:

Methods and means are implemented along a motorway in direction towardsa city with principally increasing traffic closer to the city during themorning rush hour, where the system principally is using only level Onefor control of an upstream access, where the total traffic is relativelysmall, and the system is using principally combinations of level One andlevel Three for a downstream access, where the traffic is small and therequirements are large for a well flowing traffic, and when higheffectivity is needed, the system can be complemented with level Twoupstream this access, and in certain cases, the system can be equippedfor the access with principally a combination of level One and levelFour, and alternatively the system for the motorway can be introduced invarious ways e g by using mainly only level Four or One on one orseveral accesses, and the system can also, when needed, be equipped foran access with all level, applied to an applicable extent.

Means and methods concerning level One, where the motorway and theaccess flows are controlled in relation to targets and rations for shortand longer time periods, and for short time periods a correspondingpacket or cars can be predicted to reach downstream accesses at earlieror later time stamps, and for those accesses, the allocation of accesstraffic can be corrected considering the upstream observed deviation, eg if there is observed a larger or smaller volume of cars travelling,the next following access, or if the need for compensation is larger foranother access, that access is allocated a compensating ration, thetraffic being successively readjusted along the motorway for thosedeviations, that anyhow can arise in spite of the control, especiallyseen over short time periods, and seen over longer time periods, two ormore short ones, the respective access is obtaining compensatingallocations, dependent on allocation deviations from earlier periodscompared with the valid targets and rations, and the valid target andration can successively be updated, alternatively automatically by thetraffic management system, which is supplying input data based on thetopical needs at the road network.

Means and methods concerning level Two, where the extra intermediatelane (Int) is implemented between Le and Ri lanes, and cars in Le, whichare going to exit, (A)-cars, give signs e g with blinker, and the carbehind, (B), in Ri is also giving sign and follows after car (A) on Int.and alternatively also the car (C) after (B) in Ri can be controlled,and the weaving zone for Int is utilized to prepare gaps for saferweaving, and the system can be expanded with one or more addedfunctions, e g by information means controlling the choice of lane, e gInt or Ri, and e g identifying the (B)-car, identifying the (A)-car,alternatively by detecting the signal from the (A)-car, and e g usingknowledge about this level Two process for prediction of downstreamtraffic for control of the following access.

Means and methods, where the system contributes in effectively packingthe traffic in Le lane, by estimating short term traffic density frommeasurements, and from the result appoint (B)-cars in Le, which aregiven the task to take out gaps ahead, and that process can be preparedalready before the weaving zone, and cars in Ri experiencing gaps forthem in Le, can take on the role as (A)-cars, e g showing that withblinker, and if there is an Int lane, select that lane for furtherweaving together with (B) to Le lane, and if there isn't an Int lanethey can directly weave into Le in the gap ahead of (B), and the systemcan be expanded with one or more added functions; as giving informationfor identifying also (A)-cars, and as giving information to (B) abouttaking out a suitable gap in front of (B), and as using knowledge aboutthis process for prediction of downstream traffic for control of thefollowing access.

Means and methods concerning level Three, where the system helps(B)-cars in taking out gaps, and makes adjustment of the related (A)-carcontrol, by e g correction of the ramp signal status, or alternativelytimely control of (A) for arrival to the weaving zone, or both incombination, or alternatively by timely control of (B) or (B) and (A) tosynchronize the arrival to the weaving zone, and the system can beexpanded with one or more added functions; as giving information also tocars behind (B) to handle the consequencies of (B)'s actions e gbraking, and as providing speed adjustment with dynamic signs before theweaving zone, dependent on matters as traffic density or accident risk,and lane separation lines can be added for weaving control between themotorway lanes, e g not allowing weaving from Le to Ri next to and atthe ramp.

Means and methods concerning level Four, in the case when car (A) hasreached the ramp and is travelling in parallall with RI lane, car (A) issearching for a position in front of a suitable (B)-car, and givessignal with blinker, showing that (A) wants to weave, and (B) isanswering with sign, e g the opposite blinker, and (B) is turning intothe ramp after (A), and the car (C) in Ri after (B), is respondingtaking out gap to (B), and the ramp-lane is used for the process oftaking out gap distances, (A) is adapting to his gap to the car ahead,(B) is taking out his gap to (A), and then (A) and (B) together areweaving into that gap in Ri, which has been prepared by (C), and thismethod is used when level Three has not performed the correspondingfunction, or it is used as a final step in combination with level Three,and the system is equipped with one or more added functions: asidentifying (B) and showing it for (B), and as showing the relativeposition of the gap for (A), and as showing the situation for (B)including gap size related to appropriate gap size,, and/to the relativeposition of (A), and as showing for (A) that the weaving process has tobe stopped, possibly with a reference to a return road.

Means, where the ramp is designed with two weaving zones, the first oneconcerns weaving of (B)-car to the ramp and the second one concernsweaving of (A) and (B) to Ri lane, alternatively designing the ramp witha return road for access cars or both those alternatives in combination.

means, where speed limitation is an added function in the system forselectable use on the levels Two, Three and Four, and the speed messagecan be static, e g valid for some time periods or dynamically changable,depending on time of day and/or traffic situation, the velocity being anessential parameter in the access control, and the speed information isgiven by the system in a certain design, as part of an integratedinformation, and in another specific design information is givenindirectly, e g by symbols showing a car position relative a selectedcompared position e g the position of another car.

Means and methods, where the system is equipped with system and functioncontrol, including estimating the real result of what traffic might looklike from measurements, and compare that with the target for the systemprocesses, wherein there are included the use of rules, predictions andmanagement, successively updating functions and algorithms, and/ordetection of deviations, which indicate or are estimated to give rise todangerous situations and possibly risks for drivers to break rules.

Means, where the design of the information presentation means, are givenby the following alternative basic concepts; the means including simplesymbol signs as lamps, turning on and off, prisms turning, etc. wherethe rule simply is that the car (driver) obtaining signal saying“(B)-car” is appointed (B)-car and shall fulfill his stipulated task; ie principally take out gap to the car ahead, offering (A)-car to weaveinto this gap, the (A)-car e g an access car, alternatively the meansincluding more detailed information, using illustrating symbols, as e garrows modelling a car from the right turning into the gap in front ofthe appointed car, alternatively with a more detailed informationmarking the gap in front of (B), and alternatively relating the gap tothe actual gap or using symbols for increase or decrease of the gapsize, and alternatively using symbols for limiting or decreasing thevelocity, with the objective of changing the gap and/or the arrival timeat the weaving zone.

Means, where the system controls the arrival time of the (A)-care at theweaving zone by using functions, where one alternative consists of aspeed control of (A), including the speed value zero, and successivelymanage (A) from the start of the acceleration road segment to theweaving zone by information means, in an alternative embodiment themeans includes a light source with a lobe successively swept in front of(A) at a smoothly increased speed, with (A) can follow in about the sameway as following a car, or alternatively using marks at the road side,which successively are activated at the pace (A) should follow, oralternatively using speed signs with successively increasing speed,alternatively dynamically adjustable for correcting the position of (A)relative to the planned, or alternatively an embodiment, which will showif (A) is before or after the allocated travel plan by using alternativepresentation designs e g a sign with lamps in a row and with differentcolours, where the intermediate lamp is showing that the car isaccording to plan, the low lamp that the car is below and needs toincrease, and the upper lamp that the car is ahead and needs to decreasethe pace, alternatively the presentation also includes an indication onthe size of the need for change, and one can detail the process indifferent ways e g by showing to lanes on the sign with a gap ahead of acar (B) in the left lane and the relative position of (A)-car in theright lane, where a line from the middle of the gap across the rightlane indicates an ideal position, and (A) can be marked with differentcolours if (A) is before, after or in the gap, and arrows can mark theneed for change of size and direction, and the control of (A) caninclude a cooperation with the ramp-meter signal, which is controllingthe starting time of (A).

Means, where the information means are designed including a light sourcee g a lamp lightening a selected part of the road surface in front of(B)-car or (A)-car, and the light source can be designed to have one ormore radiation variables, as several colours, several lobes,controllable lobes, whereby a corresponding simple or integrated messagecan be transferred, and the system can be expanded including varioussurface conditions of the road, which transform or reflect the radiationfrom the radiator according to its characteristics, and the surface canbe given different patterns or symbols, further increasing the thepossibility for transfer of information to the car drivers, e g a symbolmeaning increase of the gap, can be shown successively on the roadsurface in the driver's view e g within the same view covering the carahead.

Means, where an (A)-car in the left lane is detected giving a signal e gblinker, which e g can be detected by a video-camera on thepredetermined distances, where (A) is initiating change of lanes, andthen the system can identify (B)-car and show the information accordingto some of the earlier described means, and for handling the selectionof Int or Ri lanes, the system can be expanded with functions appointingby arrows the (B) route and the other cars' routes.

Means, where (A)- and (B)-cars are identified and appointed, and whenreturn is going to shown for (A)-car, it is presented according to oneof the following alternatives; e g before the weaving zone two, aradiation source is used for blocking the weaving by light on the roadsurface and/or showing the route direction to the right for the return,alternatively a sign is used, which is positioned along and in betweenthe Int and Ri lanes, which in the ordinary case is showing directionleft before the weaving zone two, but now is showing direction to theright, alternatively there is a sign with a cross over the ordinaryinformation showing that weaving is no longer admitted, alternativelythat sign might be part of the continuation of the signs, which havebeen managing (A) from the access start, and in an expanded alternativethe cross over can also be performed along the whole access distance,when the system concludes that the weaving process should beinterrupted, alternatively the signs are placed above the road, andanother possible position is at the end of the access ramp informingabout continued or interrupted process.

Means, where car equipment is used for transfer of information from thesystem to the driver, and the communication can be performed usingvarious types of media, e g radio, light or infrared technology, andcommunication can be organized by road side, locally bounded links, ormore area covering means e g cellular types of radio, and here theinformation is corresponding to the earlier described and is presentedaccording to the rules for presentations in a car, which also createspossibilities to present information by sounds, avoiding disturbance ofthe driver's eyesight control of the traffic situation, and moreinformation can be transferred to the car equipment, information in itsturn processed by the car equipment for actions and for suitablepresentation, e g related to other information for the driver.

Means, where the car is equipped with distance controlling equipment,which can be fed with information about distances and contribute intaking out gaps, e g the gap for the (B)-car, and the system can beexpanded also for using the speed control of the cars, e g for controlof the travel plan of the car, where e g already at the start of theaccess segment, the (A)-car obtains information for the whole travelprocess, and also along the road, the car can have one or more points ofcontrol for possible adjustments of the continuous travel, and furtherinformation can be transferred to the car equipment for furtherprocessing by the equipment.

Examples and Basic Concepts

In the above text several examples have been given on the accesscontrol. The purpose with the examples are illustrating the principalconcept and the basic ideas. The details of the embodiments can bevaried in many ways, which should be evident for one knowledgable in thefield. Throughout the text there are used the notation “car” e g “showfor the car”. “information to (B)-car” etc. where it is understood thatit is the driver of the car or possibly a receiver equipment in the car,which is the information receiver.

The patent thus concerns the principal concept, and examples onsolutions are submitted, which are representing also closely relatedvariants. E g the typical case is described; a motorway with two lanes,one direction, and right side driving. The invention however is possibleto apply also on motorways with more lanes and left driving. Also otherlarge roads, with one or more lanes will be applicable for most of thegeneral concepts.

The patent application touches a field, which is very little developed,but very essential. The traffic management area is also verycomplicated, as the traffic is related in a network and single actionsin one point, might often give rise to large problems at other places,than those ones considered. The access control, ramp-metering, which isused today have large shortcomings. That means that from todaysituation, improvements can be introduced on many different levels,which each one is an improvement, seen from the present situation, andthus each one can be implemented. The system has been divided into anumber of levels, and can be implemented and expanded in variouscombinations. Also various accesses along a motorway, are loadeddifferently and have different needs for solutions, and not at leasteconomic reasons, resources and timing imply different use of the systemlevels and variations as well in position and time. However, thecombination of the system levels offers an integrated coordinatedsolution on the access control to a motorway, and the system is justsuch a network based solution that is needed, but up to now has beenlacking within the traffic management area.

What is claimed is:
 1. A method concerning systems for access control oftraffic at motorways and larger roads, where the access flow iscontrolled by information means, which directly or indirectly influencethe access travel of the cars, and where the flow size is determinedconsidering the flow size on the motorway, and where cars (A) from theaccess road interact with cars (B, C, etc) on the motorway while weavingtogether the respective flows, comprising; limiting the flow of A-carson the access road by a given target value, an allocated ration, whichis related to a target value for the motorway flow, dynamicallycorrecting the said ration based on at least one of the following (a)and (b); a. upstream measurements of traffic flow on the motorway, witha correction determined by the deviation between the said flow targetvalue and said measured value, and where the said upstream measurementsite is positioned a distance L1 from the access weaving zone, where L1is that far, that flow-corrected access cars reach the motorway in timefor weaving with those motorway cars, which have caused the flowcorrection, and where a target value for L1 is L1 ≧v²/a, where v is anapplicable velocity value for the motorway and a is an applicableacceleration value for the access, and the qoutient v²/a is covering (islarger than) the corresponding quotient of velocity and accelerationvalues for most of the applicable traffic situations, b. at upstreamexit, measurements on cars, which indicate exit, a roadbased equipment,which register information about the cars indicating exit, saidinformation is used for estimating a correction of the downstream accessflow, and the traffic density in the right lane of the motorway, on adistance L2 closest upstream the weaving zone for the access, where L2is less than L1, is determined within a limit in accordance to thataccess flow, which is estimated for the weaving together with the saidmotorway traffic, including determination of target values for gapsbetween motorway cars, where said target values give a density betweencars on the motorway, which seen over the corresponding access flow timeperiod for two consecutive (A)-cars, is corresponding to an added gapfor those motorway cars, giving space for at least one car, an accesscar.
 2. A method according to claim 1, where the method includes aprincipal function, HF1, superior access control, which concerns anintegrated access flow control for a plurality of accesses along amotorway, HF1 comprising: selection of a plurality of accesses along amotorway, determination of target values for motorway flows and accessflows along the motorway, whereby each selected access is allocated adynamic ration of traffic flow for access to the motorway, measurementsof flows by sensors on the motorway, which including the access flowgives the added flow downstream the access, comparison of the actualflow on the motorway obtained from measurement, and the correspondingtarget value, and at deviations larger then a selected level; acorrection is made, Cu, of the flow ration for at least one ofdownstream accesses, where the flow is increased or decreased dependenton the upstream motorway flow being too small or too large, and there isa succeeding correction, C1, of the flow rations for accesses thatearlier have been given larger or smaller rations than the given targetvalues, a dynamically updating of allocated rations of accesses flowsbased on measured or predicted traffic situations, an updating of saidtarget values based on changed needs at the road network.
 3. A methodaccording to claim 2, where the method includes a principal function,HF2, exit control, which concerns control of exit traffic andpreparations for the following access, HF2 comprising: the exit processis performed in at least two stages, a first stage upstream of theweaving zone, a second stage, the weaving stage, where exit weaving isoccuring, and during the first stage, information is exchanged betweencars and road based equipment, where cars are indicating turning to theright or the left, the road based equipment registrating the turninginformation about the cars, information is calculated or predicted onthe resultant distribution of traffic flow, concerning primary the rightlane downstream the exit, and is used for estimation of correction ofthe downstream access flow, estimation of information about which carsselected for which lane, the road based equipment informing carsselectively about respective allocation of lanes, before or at thelatest in stage 2, and in the second stage, an intermediate lane isimplemented, Int., between the two rightest lanes of the motorway, ofwhich the most right one, Ri, at least partly might consist of theearlier implemented exit ramp, and the other, Le, also consists of theleft lane of a motorway with two lanes, single direction, and the saidroad based equipment is informing cars selectively about respectiverole, including allocation of lane, during the first or at latest duringthe second stage, comprising; cars in Le, which are going to shift toRi, are informed about the role involving a direct selection of the Int.lane, and after that weaving to the Ri, cars in Ri, which are going toshift to Le, are informed about the role involving weaving to Int. andthen further to Le.
 4. A method according to claim 1, where the methodincludes a principal function, HF3, preparatory access control, whichconcerns traffic control upstream an access, HF3 comprising: road basedequipment, is supplying information to cars on the right lane of themotorway about gap to the car ahead, where the road based informationmeans are positioned on the distance L2 or the distance between therelated exit and access, and the gap information is based on the targetvalue of the gap between cars in the right lane of the motorway, basedon estimated access flow of cars from downstream access to the motorway,determination of the target value for the gap according to (a) plus atleast one of the following criterias (b) to (e), (a). the target valueshall give a density of cars on the motorway, seen over thecorresponding access flow time period, which corresponds to an addedtotal gap, which have room for at least one more car, an access car;(b). a succession of cars are given the same information, correspondingto equal gaps, (c). dedication of gaps for cars in a row, where thefirst one or few first cars are allocated larger gaps than the nextfollowers, and the first cars are selected to match the later weaving byan access car, (d). the target value is selectively chosen from (b) atlarge access flows or long distances down to the access, while (c) isselected at smaller access flows or at short distances down to theaccess weaving zone, (e). the target value for the gap is dedicated tothe car (B) on the motorway, which is selected to let in a car (A) fromthe access, comprising; successive detection and registration of cars(A) on the access and cars on the motorway, prediction of when (A) reachthe weaving zone and selection of the car (B) on the motorway, which ispredicted to reach the weaving zone next after (A), selectiveinformation to (B) about the gap for letting in (A).
 5. A methodaccording to claim 1, where the method includes a principal function,HF4, local access control, which concerns control at the local access,HF4 comprising road based equipment, which detects and registrates cars(A) on the access and cars (B) and (C) on the motorway upstream theaccess, where the car (B) is the car on the motorway which is going tolet in car (A) ahead, and car (C) is following (B), prediction of (A)'sand (B)'s travel towards the weaving zone, whereby the selection of(B)-car is based on the said prediction, road based equipment, whichupstream the weaving zone, is informing the (B)-car about its role inthe weaving, comprising at least one of the following method steps; (a).informing about the role weaving together with (A) in position upstream(A), (b). informing about the role carrying out lane-shift to a positionbehind (A) in the ramp-lane and (B) following (A) to the weaving to theleft, i e back into the gap, which (B) left on the motorway, (c). inaddition to (b), informing (C) about the role meaning keeping the gap tocar (B), also while (B) is in the parallall lane relative to C.
 6. Meansfor carrying out the methods according to claim 1, concerning systemsfor access control of traffic at motorways and larger roads, where theaccess flow is controlled by information means, which directly orindirectly influence the access travel of the cars, and where the flowsize is determined considering the flow size on the motorway, and wherecars (A) from the access road interact with cars (B, C, etc) on themotorway while weaving together the respective flows, including trafficmanagement system, (TMS), traffic sensors and access equipment,comprising; a computer based traffic management system being fed withinformation about flows from various parts of the motorway and itsconnections to the neighbouring road network, and rations and targetvalues for traffic flows on the accesses and the motorway, beingdetermined and stored with support from the traffic management system,and dynamic corrections being estimated by TMS or by an accessequipment, and at least one of (a) and (b) being included; (a). a sensorbeing positioned the distance L1 upstream the access weaving zone,measuring the flow continuously and transmitting the traffic informationin short time intervals to the TMS and/or the access equipment, (b). anexit equipment including; sensors, detecting cars selecting to take offfor the exit, a computer unit, being positioned at the exit equipment orat the TMS, computing or predicting the traffic flow in the right lanedownstream the exit, and transmitting traffic information in short timeintervals to the TMS and/or the access equipment, an access equipmentbeing positioned at the access, including sensors for trafficmeasurement and control means for flow control at the access, andrations and correction values are obtained from TMS, or the correctionsare estimated from obtained basic values, and the access equipment ismanaging the corrected access flow, a computer unit in the TMS, theaccess equipment or a gap-information system is calculating the targetvalues for gaps for the motorway traffic in the right lane, seen overthe access flow time period; selectively combined with a gap-informationsystem positioned closely upstream the access along the motorway, thegap-information system informing motorway cars about gaps, based onobtained information.
 7. Means according to claim 6, concerninginformation from cars to road based equipment and means, comprising: aninformation transfer including at least one of the following informationtransfers; (a). the respective blinker of the car for delivering turninginformation, video sensor for the road based equipment detecting theturning information, (b) radiowave communication between car androadbased equipment, including transfer or turning information andsupplementary information for identification.
 8. Means according toclaim 6, for carrying out method steps concerning information from roadbased equipment to selected cars, comprising: information transfer witha light-lobe, which is controlled by road based equipment and positionedover the car and/or viewable for the driver on or ahead of the car, andincluding at least one of the following information transfers; (a). thelight has a selected colour, with a meaning according to given colourcode, including identity, of which the following are detailedembodiments of given information in the said claims: (a1) you are the“the colour”, (a2) you have the “the role”, (a3) you are “(B)-car”, (b),the identity colouris connected to the road based information signs withselective information regarding the corresponding indicated identitycolour, (c). the position of the light-lobe and at least one of shapeand colour give information about the controlled gap, (d) the colourcode above is changed to or combined with modulation of the light orinfrared “light”, which is detected by a car equipment.
 9. Meansaccording to claim 6, for carrying out method steps concerning effectingthe gap, comprising: cars equipped with gap controlling equipment, whichis fed with information about the gap, and is contributing in effectingthe gap.
 10. Means according to claim 6, for carrying out method stepsconcerning prediction or flow control of access traffic, comprising:cars equipped with speed control equipment, which is used for control ofthe (A)-car travel plan along the access road, based on information fromthe road based equipment.
 11. Means according to claim 6, for carryingout method steps concerning information from road based equipmentselectively to cars along a road, and which means includes presentationmeans positioned at the side of or above the road, comprising: selectiveinformation is directed to the car concerned; and is activated, when thecar ahead isn't seeing the information, and is turned off or changed,when the concerned car no longer is seeing it, and an embodiment isincluded, where the activity period at dense traffic principally isdetermined by the respective car passing the information means,selective information is given by one or more repeated presentationmeans along the road; and at repetition; the content is matched for therespective car travelling from presentation means to presentation means,and whereby information is repeated or successively varied, selectiveinformation is presented in at least one of the following ways (a)-(c);a. by an individual presentation means, b. successively, part by part,utilizing a plurality of presentation means, c. by at least two steps,where the said presentation means information is including an identityinformation, and where selective additional information is presented byanother more general presentation means, which is showing the additionalinformation related to the respective car identity information. 12.Means according to claim 6, comprising: presentation means presentingselective information, including identifying, according to at least oneof; a. light means, lamps or LED, which are changing colours, or a groupof such with different positions and colours, which are switched on indifferent combinations, (b). showing different patterns or symbols. 13.Means according to claim 6, which have a task including presentinginformation about gaps, comprising: presenting information according toat least one of (a)-(d); a. gaps are illustrated with symbols, where thereal given gap is marked related to the status of the recommended gap,the target gap, b. increasing gap is illustrated with symbols, c. statictext is indicating gap, and dynamic text or symbols are shown containingthe message increase, d. a static sign positioned upstream thepresentation means is informing about those latter means.
 14. Meansaccording to claim 6, for carrying out method steps concerning exits,and where the means include road constructions including a section ofthe motorway with its exit, where the motorway section upstream anddownstream is connected to the two right lanes of the motorway, wherethe lane most to the right is called Ri, and the other Le, comprising:the motorway section is considered divided into at least three stages; afirst stage, where the two said right lanes, Le and Ri, are separated togive space for a lane in between, Int, where the separation starts witha continuous line, or a corresponding separation between Le and Ri, andthe line is following Ri, while Le is branching to a continuous Le andInt, and a dotted line, or corresponding separation, is separating Lefrom Int, and with a traffic function, in which cars in Le can choosethe Int lane directly, while cars in Ri have to wait for weaving intoInt, until the continuous line is ended, a second stage, where thecontinuous line separating Ri and Int is changed into a dotted line; andwith a traffic function, in which cars from Ri can weave into Int, andlater on continue weaving into Le, and cars from Le, now in Int, canweave into Ri, and where Ri is branching to an exit in this stage, or atlast in the next (third) stage, a third stage, where Ri is branched intoa branch, which is constituting an exit from the motorway, if thiswasn't done in stage two, and a branch, which is combined with Int to alane, which is constituting a continuation of Ri, for connection to theright lane of the motorway, and where the length of the second stage iscorresponding to the length of traditional weaving zones, while theother stages can be done shorter, and has the road construction atraffic function, in which cars in respective Le and Ri of the motorway,which want to change lanes, can be performing that in two stages byfirst changing to an intermediate lane, Int lane, whereby trafficdensity in Le and Ri are decreasing, and weaving in from Int issimplified, compared with the weaving in dense traffic directly betweenLe and Ri.